JPH0825055A - Spot welding method with robot gun and equipment therefor - Google Patents

Abstract

PURPOSE:To eliminate the fruitless time of supplying and exhausting the air pressure to an equalizing device and to improve the continuous spotting speed by compensating the equalizing action of the total gun with the program of action control in the time of abutting and pressing to a work. CONSTITUTION:A C-gun is moved to an welding point, a work W is inserted between upper and lower electrodes 9, 7. The total C-gun is lifted with a robot, and the lower electrode 7 is made in contact with the work W. The compensation of the wear amount of the electrode is executed with the action of the program of robot. The total gun is lifted more, and the equalizing amount e of the deflection amount of a gun arm 6 and the position slipped amount of the work W is followed up. The upper electrode 9 is moved synchronizing to the movement of the lower electrode 7, the work W is applied with a prescribed pressurizing force, energized, pressed and welded. In such a way, a positioning cylinder of the equalizing device becomes needless.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spot welding method and apparatus suitable for increasing the continuous welding spot speed by a robot gun.

[0002]

2. Description of the Related Art Conventionally, when spot welding is carried out using an industrial robot, if the positioning cylinder of the robot gun is misaligned, the gun arm side electrode, that is, the fixed side electrode, causes a spring force to balance the gun weight. It is pressed by the rod side electrode, that is, the movable side electrode, comes into contact with the work (object to be welded) in advance of the movable side electrode, and prevents the work from being deformed by the inertial force of the movable side electrode. At the same time as the opening, the positioning cylinder operates to normally open the fixed side electrode.

[0003]

Conventionally, in the welding method of this type, in many cases, the controller of the robot sends a pressure signal from the welding timer directly to the gun, but in this case, the switching valve of the positioning cylinder is used. There is a factor that delays the welding spot speed because it requires an operation time to bypass the air path by sending a signal to the valve and switching the valve to supply or exhaust air.

Further, in the prior art, the amount of equalization includes the reduction amount of the electrode, and the amount of change in spring force for balancing the weight of the gun becomes large. In addition, if the posture of the gun in the direction of gravity changes to different colors depending on the position of the hitting point, it becomes difficult to balance the weight and the work may be deformed. That is, it takes a long time to discharge the air from the positioning cylinder, and the work may be deformed due to the impact force when the movable electrode comes into contact with the work or the strength relationship between the weight balance spring and the work.

[0005]

In order to solve the above problems, according to the present invention, a spot welding gun having a pair of electrodes is mounted on an industrial robot, and the gun is walked according to the operation sequence of the robot. When pressure welding is performed while inducing to the welding point position of, the movable side electrode or the fixed side electrode moves ahead of the work piece, or the operation is synchronized with the movement of the other electrode. (EN) A spot welding method whose main feature is to compensate an equalizing operation of the entire gun by a motion control program when pressure welding is performed by bringing them into contact with each other and abutting against a workpiece.

According to another aspect of the present invention, a spot welding gun having a pair of electrodes is mounted on an industrial robot through an equalizing device, and the gun is guided to a welding welding position of a work according to the operation sequence of the robot. However, when pressure welding is performed, either one of the paired electrodes is moved ahead of the work, or both electrodes are brought into contact with the work at the same timing with synchronized operation to perform pressure welding. In a welding device for compensating the entire equalizing operation by a motion control program, the equalizing operation is compensated by an equalizing device that does not include the wear amount of the electrode tip within the allowable equalizing operation range. To do.

[0007]

[Operation] Therefore, the method of the present invention has realized a high-speed spot welding system that significantly shortens the welding tact time even when the robot gun is equipped with an equalizer or not.

The equalizing amount by the conventional equalizing device is compensated by a program operation for operation control or the like so that either one of the two electrodes scoops or pushes the work. This eliminates the need for the positioning cylinder provided in the conventional equalizer, increases the continuous shot speed, and enables welding regardless of changes in the gun attitude in all directions.

Incidentally, the scooping operation here is irrespective of the posture change of the gun body in all directions, and for example, when the gun is in the downward posture, it is an operation of lifting from the lower side of the work or pushing it down from the upper posture. In the case, the operation is to push down from the top of the work, and in the case of a sideways (horizontal) posture, the operation is to push in from either the left or right.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic view of the entire spot welding robot for carrying out the method of the present invention. Further, FIG. 2 is a diagram for explaining the operation of the method of the present invention.

In FIG. 1, reference numeral 1 denotes a robot body.
The robot moves on six axes of X-axis, S-axis, Y-axis, Z-axis, R-axis and Θ-axis. Reference numeral 2 is a wrist shaft of a joint, 3 is a robot arm connected to the wrist shaft, and 4 is a spot welding gun connected to the wrist shaft at the tip of the robot arm.

The target spot welding gun 4 is, for example, C
Not only the gun but also any X-gun or a spot welding gun such as a rotary gun in which a reduction gear is interposed in the main shaft is applicable. The pressurizing device 5 for each gun is not limited to an air cylinder, but a mower.
You can In the case of a C gun, as shown in the drawing, a fixed side electrode 7 attached to one end of a gun arm 6 and a piston rod 8 of a pressurizing device 5 attached to the other end of the gun arm 6 are shown in the figure. A movable side electrode 9 attached to the robot arm 3 and is directly supported by a gun bracket 10 connected to the wrist shaft 2 of the robot arm 3.

Although the robot controller is omitted, a general robot control system based on teaching playback control or numerical control method is adopted. The control panel for the 7th axis may be either in the robot control panel or as a separate control panel.

Next, the operation of the present invention will be described. In FIG. 2A, the C gun is moved to the hitting position, and the work W is inserted between the opened upper and lower electrodes.

In the case of FIG. 1B, the entire arm of the gun is moved by operating the wrist shaft 2 of the robot arm 3 so that the fixed side electrode 7 on the gun arm side comes in contact with the movable side electrode 9 on the rod side. lift. The amount of wear of the electrodes is compensated by the operation of the robot program after each chip dressing.

In FIG. 1C, the robot arm 3 further lifts the entire gun to follow up the equalization amount e between the deflection amount of the gun arm 6 and the work position deviation amount. That is, in the gun arm itself, the fixed-side electrode 7 hooks the work W from below from within the allowable range of work deformation and scoops it up.

In FIG. 3D, the fixed side electrode 7 is backed up in a state of being scooped up while the movable side electrode 9 is brought into contact with the fixed side electrode in a movement synchronized with the movement of the fixed side electrode, and a predetermined pressurizing force is applied to energize. Pressure welding. At the time of this welding, the gun arm moves as a part of the 1st axis to 6th axis of the robot body to operate the piston rod 8 of the pressurizing device 5 for the 7th axis without applying a load to the work, The necessary pressing force is applied between the movable electrode and the fixed electrode to press the hitting point. In this way, by using the motor as the pressurizing device, the movement of the fixed side electrode (1st to 6th axes) and the movement of the movable side electrode (7th axis) are synchronized to perform the equalizing operation, so that the upper and lower electrodes are covered. Matching the timing of contact with the welded material enables even higher-speed spotting.

In the case of the embodiment shown in FIG. 2, the work is scooped up by the fixed side electrode. However, as shown in the example of FIG. 3, the upper surface of the fixed side electrode has a gap with respect to the work due to a teaching mistake or the like, or the work is intentionally performed. Even if it is pushed down by the movable side electrode, it does not matter if the gap amount is within the elastic range of the work.

2 and 3, the equalizing device that can move the entire gun up and down by several millimeters is omitted, but when the elastic allowance of the work is smaller than the pick-up amount e ₁ or the push-in amount e ₂ by the electrode. In order to prevent plastic deformation of the work, an equalizer is attached as shown in FIGS.

In the equalizing device shown in FIG. 4, as an example, the equalizing shaft 11 of the gun bracket 10 supports the gun support 12 in a movable state, and the weight balancing spring 13 is inserted in a direction balanced with the weight load of the entire gun. It is a thing. This spring 13 is omitted in the device of FIG.

In this case, what is different from a general equalizing device is that the wear amount of the electrode tip is not included in the equalizing amount and the allowable equalizing range is kept to a minimum so that it can be handled (when the robot is moving). The rattling of the welding gun can be reduced and the impact on the workpiece coming from the rattling at the time of picking up and pushing can be softened.

FIG. 4 shows a series of operations for picking up the work W by the fixed side electrode 7 and performing pressure welding. In this case, the equalizing device has a clearance c necessary for the operation of the equalizing amount e _{1 in} the scooping direction. It is provided.

FIG. 5 shows a series of operations in which the work W is pushed by the movable electrode 9 and pressure welding is performed. In this case,
The equalizing device is provided with a clearance c necessary for the operation of the equalizing amount e _{2 in} the direction of pushing down by the movable side electrode 9.

[0024]

As described above, according to the method of the present invention, when welding is performed using the robot gun, the equalizing operation of the spot welding gun is compensated by the operation control program, and therefore the robot side The workpiece is lifted up or pushed down by one side of the electrode to back up, and the other side of the electrode is brought into contact and pressure welded in synchronism with the synchronized movement. Since the positioning cylinder of the equalizer is not required, the wasteful time of operating the air pressure supply or exhaust without deforming the work is eliminated, and both electrodes operate in synchronization to increase the continuous shot speed. .

Further, the amount of wear of the electrode tip is compensated for in the program, and the amount of deflection and the work of the gun arm is increased by the operation of picking up or pushing down the work side by the electrode on one side by the movement of the robot. It is possible to compensate for the equalizing operation including the amount of positional deviation of the workpiece, and to weld the work without deforming the work regardless of the posture change of the gun in all directions.

According to the apparatus of the present invention, an equalizing device is attached when the work elastic allowable amount is smaller than the scooping amount and the pushing amount. However, since the positioning cylinder of the equalizing mechanism is unnecessary, the robot gun can be made smaller and lighter. Achieves simplification of structure and reduction of manufacturing cost.

[Brief description of drawings]

FIG. 1 is a schematic view showing an entire spot welding robot for carrying out the method of the present invention.

FIG. 2 is an operation explanatory view of the method of the present invention, showing an operation example in which a work is picked up by a fixed electrode and pressure welding is performed when an equalizer is not used.

FIG. 3 is an operation explanatory view of the method of the present invention, showing an operation example in which a work is pushed in by a movable electrode and pressure welding is performed without using an equalizer.

FIG. 4 is an operation explanatory view of the method of the present invention, showing an operation example in which a work is picked up by a fixed electrode and pressure welding is performed when an equalizer is used.

FIG. 5 is an operation explanatory view of the method of the present invention, showing an operation example in which a work is pushed in by a movable electrode and pressure welding is performed when an equalizer is used.

[Explanation of symbols]

1 Robot Main Body 2 Wrist Axis 3 Robot Arm 4 Spot Welding Gun 5 Pressurizer 6 Gun Arm 7 Fixed Side Electrode 8 Piston Rod 9 Movable Side Electrode 10 Gun Bracket 11 Equalize Axis 12 Gun Support 13 Weight Balance Spring e ₁ Scooping e ₂ Push down amount c Clearance W Work

Claims (2)

[Claims] 1. When a spot welding gun having a pair of electrodes is mounted on an industrial robot and pressure welding is performed while guiding the gun to a welding point of a work according to the operation sequence of the robot, Of the entire gun when either one of the electrodes forming the lead moves ahead of the work, or when one of the electrodes contacts the work at the same timing with the operation synchronized with the movement of the other electrode to perform pressure welding. A spot welding method using a robot gun that compensates the equalizing operation with a motion control program. 2. A spot welding gun having a pair of electrodes is mounted on an industrial robot via an equalizing device, and pressure welding is performed while guiding the gun to a welding spot position of a work according to the operation sequence of the robot. To the work piece, either one of the paired electrodes is moved in advance of the work piece, or both electrodes are synchronized and the timing is matched to bring the work piece into contact with the work piece for pressure welding. In a welding apparatus for compensating by an operation control program, the equalizing operation is compensated by an equalizing apparatus that does not include the wear amount of the electrode tip within its allowable equalizing operation range.